The pumped storage is a mechanism for using electricity generated at night and off peak hours to pump water up to a resevoir. During peak hours, the water can be released back to the river where the hydroelectric generators produce electricity.
Nuclear generators can’t be throttled so pumped storage along with a nuclear plant is an ideal solution.
A good example of success are the Sequoyah Nuclear Plant, the Racoon Mountain Pumped Storage facility and the Nickajack Dam.
Except when the powers to be do not want nuclear power plants like say.... Germany.